1. Field of the Invention
The present invention relates to a surface inspection system for elongated work boards (elongated boards to be worked) such as building boards, and in particular, to a system for automatically inspecting the surface of work boards that have been treated in each manufacturing process.
2. Description of the Related Arts
In the conventional continuous coating line of work boards for instance, a large number of raw boards to be coated are placed one by one onto the working line in predetermined time intervals so as to successively execute various sequential workings thereof including a back surface coating process (using a sealing paint), a drying process, a surface undercoating process (using a sealing paint), a drying process, a surface intermediate coating process (using a concave portion color paint), a drying process, a surface top coating process (using a convex portion color paint), a drying process, a clear coating process, and a drying process, thus obtaining the finally coated building boards. The surface of the work boards after being treated in each coating and drying process exhibits a specific surface color. However, these specific colored surfaces after each process are scarcely inspected. Namely, the inspection process is usually arranged at the final stage in the aforementioned continuous coating line, so that the inspection of the building board is usually performed for the final products in that continuous coating line. Therefore, the evaluation of the continuous coating work at each manufacturing process is inevitably determined by simply observing the surface with operator""s naked eyes.
One of the reasons which make it difficult to perform the inspection of the surface of the work boards on the way in continuous coating line is assumed to be as follows. Namely, in the case where the inspection process is to be performed at the final stage, all manufacturing processes of continuous coating line has been already finished, so that it is possible to precisely transfer the building board, the both ends thereof being guided by guiding members for instance, onto a predetermined position at an optimum velocity, thus making it possible to take a picture of the surface of the building board by making use of an inspection TV camera which has been installed just above the predetermined position.
Whereas if the inspection is to be performed on the way in the continuous coating line, means for controlling the work boards so as to enable them to move over a predetermined position is required to be installed all along the transferring line of the work boards which are to be individually transferred at a high velocity (40-60 m/min.), thus requiring an enormous cost for the installation. Additionally, it is often required, at the occasion of transferring the work boards from one working process to the next working step, to inevitably change the moving direction of the work boards in conformity with the layout of factory. In such a case, the moving velocity of the work boards is also often required to be changed. As a matter of fact, it is very difficult in such a case to render the work boards to move at a fixed velocity and over a fixed location only for the purpose of inspecting the work boards at each working step. If there is a location where the movement of work boards (building boards) is temporarily stopped in the transferring line, it would be possible to take the picture of the entire surface of each elongated work board by making use of a plurality of digital cameras so as to obtain the image data of the work board. However, if the opportunity of obtaining the image data of the work board is limited to such a resting location in the transferring line of the work boards, it is impossible to perform the inspection of the work boards at each of the working processes.
Generally speaking, the field where an inspection TV camera can be employed is limited to a situation where it is to be employed for observing a sheet-like body moving continuously at a fixed velocity, or to a situation where it is to be employed for watching a board to detect any abnormal moving thereof. However, it is difficult to utilize an inspection TV camera in a situation where the worked surface of work boards at each working process is required to be evaluated more or less precisely.
In order to observe the surface of moving work boards, it is required to establish a technique to obtain image data of the surface of work boards by carefully taking the following unfavorable inspection conditions into consideration. Namely, the unfavorable inspection conditions are; (1) the work boards to be watched are being moved at a high velocity; (2) the work boards are subject to changes in moving velocity during the moving thereof; (3) the work boards are not necessarily allowed to move over a fixed location in the transferring line thereof; and (4) each of the work boards to be inspected is so long as 2 to 3 meters.
On the other hand, it is not preferable, in view of promoting labor saving, to adopt an idea to make an operator observe the finished condition of individual work board at each working step. Even if the operator""s observation is limited to only important processes, the continuous observation thereof is still burdensome for the operator and still more, the reliability of the judgment through the operator""s observation is not so high, especially when the moving object to be watched is lengthy such as in the case of the building boards.
The present invention has been made under the aforementioned circumstances, and therefore an object of the present invention is to provide a surface inspection system for elongated work boards, which is capable of reliably observing the finished condition of elongated work board at each working process in a continuous working line through which the work boards are allowed to move individually.
Namely, according to the present invention, there is provided a surface inspection system for work boards, which comprises a digital camera for photographing an elongated work boards, an image data-extracting means for extracting a line image data on a sampling line intersecting with a moving direction of the work boards from an output of the digital camera, and an image data-synthesizing means for integrating and synthesizing the line image data fed from the image data-extracting means.
The image data-extracting means is designed to take, as the sampling line thereof, a line which passes through an intersection point between a pair of diagonal lines in the photographing zone of the digital camera and approximately orthogonally intersects with the longitudinal direction of the work boards, thereby making it possible to minimizing a distortion of image that might be brought about by the lens of the digital camera.
The surface inspection system may be further provided with a velocity measuring means to measure the moving velocity of the work boards, and the image data-synthesizing means is designed to determine positional information of the line image data in relative to the entire body of the work board on the basis of the moving velocity measured by the velocity measuring means, thereby making it possible to obtain an image data of high precision even if the work boards are caused to change in velocity and to meander.
Further, the surface inspection system may be further provided with a slanted degree-measuring means to measure the slanting degree of the work boards, and the image data-extracting means is designed to change the sampling line on the basis of the slanting degree of the work boards measured by the slanted degree-measuring means, thereby making it possible to obtain an image data of high precision even if the work boards are caused to move slantly.
The slanted degree-measuring means is designed to measure the slanting degree of the work boards on the basis of the distance between a pair of intersection points to be formed between one straight line in the photographing zone of the digital camera and the outer line of the work board, thereby making it possible to easily determine the slanting degree of the work boards without necessitating the employment of additional detecting means.
Moreover, the slanted degree-measuring means is designed to detect an abnormal moving of the work boards and to inform an operator of the abnormal moving.